Bug: Auto sizing not working properly due to rounding error when calculating defaultCharWidth

[NiklasMelznerExxcellent]

The XSSFSheet#autoSizeColumn method doesn't work properly for some specific cell values and font metrics.

The following code snippet is an example for this behavior:

String sheetName = "Sheet 1";
String cellText = "Auto sizing incorrect! :(";

try (XSSFWorkbook workbook = new XSSFWorkbook()) {

    final XSSFSheet sheet = workbook.createSheet(sheetName);

    final XSSFCell cell = sheet.createRow(0).createCell(0);

    cell.setCellValue(cellText);

    final XSSFFont font = workbook.createFont();
    font.setFontName("Arial");
    font.setFontHeight(15);
    font.setBold(true);

    final XSSFCellStyle style = workbook.createCellStyle();
    style.setFont(font);
    cell.setCellStyle(style);

    sheet.autoSizeColumn(0, false);

    try (FileOutputStream fOS = new FileOutputStream("./test-excel.xlsx")) {
        workbook.write(fOS);
    }
}

Generated excel file:

The bug is caused by a rounding error in SheetUtil#getDefaultCharWidth:

poi/poi/src/main/java/org/apache/poi/ss/util/SheetUtil.java

Lines 301 to 302 in 5533d35

	TextLayout layout = new TextLayout(str.getIterator(), fontRenderContext);
	return Math.round(layout.getAdvance());

Rounding is not necessary at all, removing the operation and converting the return type of getDefaultCharWidth() to double solves the issue.

The column width calculation that causes the error (and uses a value returned by SheetUtil#getDefaultCharWidth) occurs in SheetUtil#getCellWidth:

poi/poi/src/main/java/org/apache/poi/ss/util/SheetUtil.java

Line 244 in 5533d35

return Math.max(minWidth, ((frameWidth / colspan) / defaultCharWidth) + style.getIndention());

[pjfanning]

I added some changes in 8819952

I didn't want to break backward compatibility so I've added new methods and deprecated the ones that they replace.

It's hard to automate tests because the calculated widths depend on the font setup that testers have installed.

If you can spot a mistake or could try out my change that would be great. I will double check the code change later and it is possible it might break a few tests.

[NiklasMelznerExxcellent]

I can't see any additional failing tests (except the ones that fail due to my locale but aren't related to the issue).
My example seems to work too:

Do you know when the next version will be released yet?

[pjfanning]

It will be a few weeks before POI 5.2.5 is released. We are concentrating on releasing XMLBeans 5.2.0 first and once that is released, we should be in a position to start a POI release vote.

[NiklasMelznerExxcellent]

Alright, thank you for addressing the issue so quickly!

[pjfanning]

@NiklasMelznerExxcellent Some users are complaining that this change is still creating cells that are not wide enough. Would you have any interest in having another look?

I'm wondering whether it might be worth just arbitrarily increasing the width of each cell by some hardcoded width. Maybe we could make this configurable but default to some non-zero value.

[niklasmelzner]

I guess you're referring to this bug?
I'll have a look at it next week.